1. Principles of Population Ecology
Population ecologists ask:
1) How many are in the population?
2) Are its numbers increasing / decreasing?
3) What is its pattern of reproduction?
4) What is its pattern of mortality?
Significance of understanding this?
Manage domestic and wild populations
Manage pests
Save Endangered Species
Understand our own population changes

2. Principles of Population Ecology
How Do Populations Change in Size?
On a global scale (closed system):

3. Principles of Population Ecology
How Do Populations Change in Size?
On a local scale (open system):

4. Principles of Population Ecology
How Do Populations Change in Size?
Global scale:
Death rate
Growth rate
r = b – d
Birth rate

5. Principles of Population Ecology
How Do Populations Change in Size?
Local scale:
Death rate
Growth rate
Emigration rate
r = (b – d) + (i – e)
Birth rate
Immigration rate
Rule of 70: 70/Growth Rate% = Doubling Time

6. J-shaped curve (exponential growth)
Biotic Potential
Maximum Population Growth-
under ideal conditions = intrinsic rate of increase
J-shaped curve (exponential growth)

7. Carrying Capacity Environmental Resistance-
Exponential growth cannot occur forever.
What factors prevent it from doing so?
S-shaped curve (logistic growth)

8. Principles of Population Ecology
Overshooting the carrying capacity can lead to a population crash.
Positive & Negative
Feedback Loops

9. Population Crash
Population 1910= 26 / 1935= 2K / crash / 1945=8

10. Reproductive Strategies
Life History Strategies
r-selected
K-selected
vs.
high growth rate
slow growth rate
small body size
large body size
early maturity
late maturity
short life span
long life span
large broods
small broods
little / no parental care
high parental care
Which are we? How do we apply this knowledge?

11. Survivorship & Reproduction

12. Density Dependent Factors
Factors that influence population growth when its density is high.
Predation, competition, disease, parasites, food availability.

13. Locust

14. Lemmings

15. Factors that Affect Population Size
Density-Dependence and Boom-or-Bust Population Cycles
Predator birth timing?

16. Predatory Prey Dynamics
Wolves Established Moose 1900 approx.
1980’s parvovirous hits wolves
1995 & 96 harsh winters and overgrazing
Tick numbers increase with warm spring & fall
Isle Royal southern limit of Moose

17. Ticks

18. Density-Independent Factors:
Regardless of population density, influences population growth.
Weather, fire, earthquakes, etc…